In an optical communication system, dispersion tolerance is in inverse proportion to the bit rate. As the bit rate increases, the dispersion tolerance of the system decreases rapidly. In the future intelligent global communication network, the add/drop and switching of channels at different nodes will be more and more complex. The receiver is unable to predict the specific path of an optical signal, and therefore the dispersion of a link is indefinite. The residual dispersion value is likely to exceed the dispersion tolerance of the system and therefore seriously impacts the performance of the system. Therefore, how to compensate for the system dispersion dynamically and efficiently becomes a hot spot of research.
In a prior art, the system dispersion is compensated dynamically according to the bit error ratio (BER, Bit Error Ratio) of the code error rate performance caused after a service is connected. Specifically:
Before the service is connected, a tunable dispersion compensator (TDC, Tunable Dispersion Compensator) performs rough tuning for the dispersion compensation and at the same time, an optical receiving module demodulates the signal. The demodulation of the signal is completed when the dispersion of the optical communication system falls within a dispersion window receivable by the optical receiving module.
After the service is connected, the rough tuning of the TDC is stopped, and the BER of the system is collected and fed back to the TDC. The TDC performs fine tuning according to the BER of the system until the fed back BER is minimum in a period of time. The TDC value then may be regarded as the best dispersion compensation value of the system. Thus, a dynamic compensation for the dispersion is completed.
During research and practice of the prior art, the inventor finds the following problems:
Because TDC tuning and signal demodulation are performed simultaneously, it is the case that the demodulation of the signal has not been completed at the same time that the TDC is tuned within the proper dispersion window of the signal, so that the service cannot be connected and the best dispersion window is missed, and then the service is disconnected. As a result, a second TDC search process is performed and the service connection time is prolonged.
The BER can be tuned only after the service is connected and error bits are transmitted. The tuning is slow and adds to the service connection time of the system.